WASHINGTON -- Newly obtained information potentially undermines a prosecution witness used to convict an illegal Salvadoran immigrant of killing former intern Chandra Levy, an unusual court hearing revealed Tuesday.

Citing "information that has come to the government's attention," D.C. Superior Court Judge Gerald I. Fisher huddled with prosecutors and defense attorneys for nearly two hours Tuesday afternoon before scheduling a follow-up hearing next month. At the prosecutors' request, Fisher kept nearly all of the discussion, including the reasons for the secrecy, sealed at a private bench conference.

"The possible disclosure of that information may create safety issues," Fisher said.

The hearing occurred more than two years after a jury convicted Ingmar Guandique of Levy's murder.

During 10 days of trial testimony, prosecutors persuaded jurors that Guandique killed Levy in Washington's Rock Creek Park on May 1, 2001. The 24-year-old Levy had finished graduate studies and a federal Bureau of Prisons internship and was preparing to return to her family's home in Modesto.